Automatic stop and timer for machine tool control



Sept. 21, 1954 c, Y 2,689,363

AUTOMATIC STOP AND TIMER FOR MACHINE TOOL. CONTROL Origixial Filed Dec.16, .1946 3 Sheets-Sheet 1 /ffl / 7 .mi in. I 5 2 i //9 i l I a? I; I II 2f fizm aior Sept. 21, 1954 c, FRYE 2,689,363 AUTOMATIC STOP AND TIMERFOR MACHINE TOOL CONTROL Original Filed Dec. 16, 1946 3 Sheets-Sheet 2C. F. FRYE Sept. 21, 1954 AUTOMATIC STOP AND TIMER FOR MACHINE TOOLCONTROL 3 Sheets-Sheet 3 Original Filed Dec. 16, 1946 26 0 NKg I 4 8 2 7Z 4 a 0 w H M I Patented Sept. 21, 1954 UNITED STATES .ATENT OFFICE ATOM TIC S AND TIMER OR MACHINE TOOL vCONTROL Cla ms- '1 My inventionrelates to automatic controls for machinery.

When it is desired to drill a blind hole to a predetermined depth, anautomatic trip that throws out a feed operating at constant speed cannotbe operated reliably to get a constant depth, and the depth ofsuccessive holes will vary by several thousandths of an inch. With theforce-sensitive timed feed according to the invention, it is possiblefor an inexperienced operator to drill blind holes, and theautomatiofeatures of the control will give holes of exactly identicaldepth with an accuracy down to precision tolerances.

This application is a division of my co-pending application, SerialNumber 716,543, filed December 16, 1946, now Patent Number 2,652,732,dated September 22, 1953.

In the accompanying drawings:

Figure l is a side elevation of a drill press;

Figure 2 is an enlarged elevation of the control box of Figure 1 withthe cover removed;

Figure 3 is a side elevation of a mechanical reset timing switch;

Figure 4 is an end view of the switch of Figure 3;

Figure 5 is a similar view, partly in section on line 55 of Figure 3.

' The conventional drill press includes the standard I0, work table II,power head- I2, and spindle I3, which may be reciprocated vertically byrotating the cross shaft I4 provided with three equally spaced radialhandles I5 for the convenience of the operator. This also activates thepivoted sector I6 meshing with thesame pinion on shaft It which engagesthe teeth of the rack I! to move the spindle It. The sector I6 alsocarries a crank arm I.8 connected by means of an adjustable pitman I8aextending down through a conventional packing 18b to connect with the pito 9 in he cylinder 251:. he yl nder may be suitably supported in andesired position as by means of a bracket 2|. The pitman IBa car.- riesan abutment 22 receivin the thrust of the compression spring 23 to holdthe parts in the position shown in the drawings.

A r er pressure may be intro uced in o h cylinder 20 to force the pistonI9 down and actuate the spindle I 3. The compressed air supplyisindicated at 38. It passes through a pipe 31 to a control box 36, whichmay include conventional pressure-reducing means, adjustable by thehandle 41, and a gauge 45, to indicate to the operator what pressure isbeing delivered through the pipe 35 and fitting 24 to the workingcylinder.

Air under pressure is received through the connector 44 and conveyedto aconventional pres sure reducing valve 46, the adjusting handle 4''! ofwhich projects through the cover of the house ing 39 to be accessible tothe operator. From the pressure reducing valve, the air at reducedpressure enters the control block 48 at the inlet 49. The gauge 45 isprovided for the convenience of the operator in knowing what pressure heis getting.

From the inlet 49 the air may find its way to the horizontal passage 50subject to control by a first solenoid valve 52. The passageway 50 always connects at 54 to the actuating cylinder and to the chamber 5%controlled by the right solenoid valve 5?. Each of the solenoids 52 and51 lifts or drops its valve element proper (see Figure 2). It will beapparent that with the left solenoid valve 52 open and the right closed,operating pressure will be delivered to the cylinder. But if therelationship is reversed, the passageway 56 no longer receives air underpressure, being out off from. the inlet 49, and functions as a dischargepassage through the chamber 56 and exhaust opening 58. The insulatingpanel It carries a fuse I9 and terminals for low voltage wiringconnections, energized by the step-down transformer 49.

Referring now to Figures 3, 4, and 5, I have indicated a microswitch H6housed in a suitable channel-shaped support I I1 and operated to openand close a circuit by pressure on the finger IIB, for transferringenergizing current from solenoid 52 to solenoid 51. To actuate thefinger I provide a timing mechanism involving an oil-filled dash-pot H9having a workin space I20 and an enlarged bore I22 above the workingspace. The plunger 52 is a loose fit in the working space I253 and isprovided with a vent passage, including a check valve 526, which permitsliquid to flow into the working chamber but not out of it. The upper endof the plunger carries a bracket I2? having a projection I28 overlyingthe end of the finger M8 to depress the same. The plunger and bracketare held up in the position of Figure 2 by a compression spring I29. Thepush rod I30 telescopes freely in the plunger I24 and carries anabutment for the upper end of the compression spring I32, the lower endof which bears on the upper end of the plunger I24.

It will be apparent that if the push rod ISO is forced down, theincreased tension of the spring I32 will result in an unbalanced forceto move the plunger I24 down, but this movement will be Thus it is easyto design the parts so that a period of from two to as much as fifteenseconds elapses before the projection I28 has moved down to the limit ofits movement. By pivoting the microswitch at I34 and adjusting itsposition with the adjusting screw I36, the position of the finger IIBmay be shifted to secure any desired delay within the capacity of thedevice.

Means are provided for depressing the plunger I30 when the tool comes tothe end of its desired path of movement. I have indicated a ball contactI31 at the upper end of the push rod I30 and a rocking lever I38 pivotedat I39. The rocking lever may be positioned where a suitable projectionfrom a tool carriage or spindle, such as the spindle I3 of Figure 1,will engage it, and is of sufficient mechanical strength to hold thespindle against movement under the force of the actuating piston. I haveindicated a heel I40 to limit the movement of the lever I38 in the otherdirection. By extending the heel I60 at I4I, convenient mechanicalcontact is provided for machine elements moving in either direction.

When it is desired to feed any tool, such as a drill, end broach ormilling cutter, so that it will cut into the work up to a predeterminedpoint with a high degree of precision, and leave a cut surface that issmooth and uniform throughout, the equipment of Figures 3, 4, and 5 maybe employed in such a way that the tool carriage moves with a highdegree of precision to a predetermined position and remains in thatpredetermined position for a predetermined time, which may amount toseveral seconds,

while the cutting tool continues to turn against the work and loaddistortions of the frame of the machine are relieved. Then, when themicroswitch is closed and the tool backs away, it will be found that thebottom of the hole or the end of the out has been finished withprecision.

It will be apparent that because the feeding instrumentality isforce-sensitive andhesitates momentarily and only exerts a predeterminedmaximum feeding force, no harm is done if the tool carrier is arrestedwith a fixed stop at any time, either to discontinue the feed or topostpone it while some other operation is taking place.

Thus, the right or left end of the lever I38 is the effective stopmember, and is displaced by contact with the spindle I3 or other toolcarriage, and the lever I38 rotates clockwise until its right endstrikes the channel I I1. This holds the spindle firmly and accuratelyin a predetermined position until the dash-pot I20 lets the finger I20get down far enough to actuate the switch lever H8, and the feed isreversed. The displacement of the lever before its limit of movement isreached stores energy in spring I32, and the gradual dissipation of thatenergy into compression of spring I29 and into displacement of the oilperforms the timing function.

Others may readily adapt the invention for use under various conditionsof service by employing one or more of the novel features involved, orequivalents thereof. As at present advised with respect to the apparentscope of my invention, I desire to claim the following subject matter.

1. Automatic timed dwell equipment for machine tools comprising, incombination with a conventional machine tool having a work supportelement and a tool carrier element; feed means for moving one of saidelements with respect to the other, including a pneumatic transmission,capable of exerting not more than a predetermined maximum feeding force;stop means including a stop member mounted on a. first one of saidelements in a position to engage and be displaced by the relativemovement of the other, second element; said stop means including a fixedmounting part rigid with the first element; a limited lost-motionconnection between said stop member and said fixed part; resilient meansbiasing said stop member toward said second element; energy-storagemeans actuated by said stop member when displaced by said other element,for storing mechanical energy; movable dissipating means connectedbetween said stop member and said fixed part, for slowly dissipating theenergy thus stored; an electric switch including an actuating elementlying in the path of movement of said dissipating means;operator-controlled means for adjusting the position of said actuatingelement in a direction parallel to the path of movement of saiddissipating means, to vary the time interval intervening after feed isstopped and before said switch is actuated; and feed reversing meansrendered operative by actuating said electric switch.

2. Automatic timed dwell equipment for machine tools comprising, incombination with a conventional machine tool having a work supportelement and a tool carrier element; feed means for moving one of saidelements with respect to the other, including a transmission capable ofexerting not more than a predetermined maximum feeding force; stop meansincluding a stop member mounted on a first one of said elements in aposition to engage and be displaced by the relative movement of theother, second element; said stop means including a fixed mounting partrigid with said first element; 2. limited lost-motion connection betweensaid stop member and said fixed part; resilient means biasing said stopmember toward said second element; energy-storage means actuated by saidstop member when displaced by said other element, for storing mechanicalenergy; movable dissipating means for slowly dissipating the energy thusstored; an electric reversing switch including an actuating elementlying in the path of movement of said dissipating means;operator-controlled means for adjusting the position of said actuatingelement in a direction parallel to the path of movement of saiddissipating means, to vary the time interval inter-' vening after feedis stopped and before said switch is actuated.

3. Automatic timed dwell equipment according to claim 2, in which saidswitch is in a housing with said actuating element projecting from thehousing, and said adjusting means operates by displacement of the entirehousing and contents.

4. Automatic timed dwell equipment according to claim 2, in which saiddissipating means is a plunger, a dash-pot receiving one end of saidplunger, and spring means normally holding said plunger in withdrawncondition, and said energy-storing means is an opposing spring posi- 1tioned to be stressed by the movement of said stop member toward saidfixed mounting part.

5. Automatic timed dwell equipment according to claim 4, in which saiddash-pot and plunger are provided with an inlet passage and an inwardlyopening check valve in said passage,

whereby the parts can return to original position quickly.

References Cited in the file of this patent Number UNITED STATES PATENTSName Date Goble Mar. 17, 1874 Hoyt Apr. 1, 1879 Tudor Jan. 8, 1884Newman Sept. 4, 1888 Gustin Oct. 9, 1888 Lawler July 14, 1908 UrquhartApr. 15, 1913 Murphy Sept. 7. 1915 6 Name Date Haderman July 16, 1929Balsiger Oct. 25, 1932 Schafer June 22, 1937 Boothroyd Mar. 15, 1938 Nyeet a1. July 30, 1940 Robinson Jan. 5, 1943 Shartle July 20, 1943 ThorpJan. 4, 1944 Somes et a1. Sept. 26, 1944 Hard at Segerstad May 27, 1947Frye Dec. 2, 1949 Hennessy Feb. 1, 1949

